Machine tools and the further objects described above are for example known from WO 03/089999 A1. They are offered for example as so-called multiple five-axis milling machines. These types of machine tool feature at least one linear axis, by means of which all machining heads are displaced translationally simultaneously and in the same way. A movement of the machining heads in other translational linear directions can alternately be impossible or be possible independently of each other. A typical embodiment of a prior art machine tool and its method of operation will be explained in greater detail below in conjunction with FIGS. 1 and 2.
In accordance with FIG. 1 the prior art machine tool has a portal 1. The portal 1 corresponds to a main support element 1 as defined by the present invention. The portal 1 is able to be positioned by means of a schematically shown drive 2 in a translational linear direction—typically referred to below as the x-direction. The drive 2 of the portal 1 corresponds to a main positioning device 2 as defined in the present invention.
The portal 1 is able to be displaced by means of the drive 2 over a region of displacement 3. The region of displacement 3 of the portal 1 corresponds to a main region of displacement 3 as defined in the present invention. It can amount to several meters.
Arranged on the portal 1 are (at least) two machining devices 4, 5. They correspond to a basic machining device 4 and an accessory machining device 5 as defined in the present invention. For the prior art machine tool the machining devices 4, 5 are embodied identically.
Each machining device 4, 5 has a basic pivot device 6, 7, by means of which a respective machining head 8, 9 is able to be pivoted in at least one rotational pivoting direction α, β. Mostly the machining heads 8, 9 are able to be pivoted in two rotational pivoting directions α, β.
It is possible in individual cases for the machining heads 8, 9 only to be able to be pivoted relative to the portal 1. As a rule however the machining devices 4, 5 however have further positioning devices 10 to 13 by means of which the machining heads 8, 9 are able to be translationally positioned in at least one further direction, with this further direction able to be positioned linearly independently—especially orthogonally—to the direction in which the portal 1 is able to be translationally positioned. Often the machining heads 8, 9 are even able to be translationally positioned in two further directions—typically referred to below as the y-direction and z-direction. Provided the machining heads 8, 9 are able to be translationally positioned relative to the main support element 1, these translational positionings only act on the respective machining head 8, 9.
Mostly the translational degrees of freedom in which the main support element 1 is able to be moved, and the translational degrees of freedom in which the machining heads 8, 9 are able to be moved independently of each other relative to the main support element 1 supplement each other to form right-angled Cartesian coordinate systems, which—depending on the position of the individual case—cover one plane or the three-dimensional space.
The above embodiment is typical of prior art multiple machine tools. However further deviations are readily possible and conceivable. Thus for example, in an alternate embodiment the main support element might not be embodied as portal 1, but for example as a support which is able to be translationally positioned along of the portal 1. In this case the main support element would be able to be translationally positioned in two directions orthogonal to each other, so that a translational positioning of the machining heads 8, 9 independently of each other relative to the main support element is either not possible or only in a single direction linearly independent of the possible translational directions of movement of the main support element. In exceptional cases it can even be possible that in all three translational directions, as a result of the design, only a common positioning of the machining heads 8, 9 is possible. This can for example be the case if the main support element is embodied as a bar able to be lowered and raised on the above-mentioned support.
The machine tool of FIG. 1 is controlled by a control device 14. The control device 14 is embodied as a rule as a motion control unit, especially as a numerical control (=CNC). A computer program 15 (system program 15) is thus stored in the control device 14. The computer program 15 has been created beforehand and fed to the control device 14. For example the computer program 15 can have been stored on a data medium 16 and fed in this way to the control device 14. The data medium 16 can in this case be embodied in any way, for example as a memory card, a USB memory stick, as a CD-ROM etc.
Alternatively to being supplied via a data medium 16 it is possible to convey the computer program 15 to the control device 14 via a computer-computer-connection 17. The computer-to-computer connection 17 can be the Internet for example.
The computer program 15 comprises machine code 18 which is able to be executed by the control device 14. The execution of the computer program 15 by the control device 14 has the effect of the control device 14 controlling the machine tool in accordance with an operating method which is explained in greater detail below in conjunction with FIG. 2.
In accordance with FIG. 2 the control device 14 initially determines in a step S1 for each machining head 8, 9 one translational linear positioning PT (T for translational) and a rotational pivot positioning PS (S for pivoting) on the basis of an application program 19. The application program 19 can for example be a subprogram in accordance with DIN 66025.
In a step S2 the control device 14 then determines on the basis of the translational linear positioning PT a translational main positioning PTH for the basic machining head 8. In a step S3 the control device 14 controls the main positioning device 2 such that the latter moves the main support element 1 to the translational main positioning PTH. Furthermore the control device 14 in a step S4 controls each basic pivoting device 6, 7 such that the latter pivots the machining head 8, 9 able to be pivoted by it into its respective rotational pivoting positioning PS.
In the example of FIG. 1, in which the main support element 1 is only able to be translationally positioned in one dimension, the control device 14 also determines—preferably within the framework of step S2—a positioning for the other translational directions, in which the machining heads 8, 9 are able to be positioned independently of each other. These positioning movements are of subordinate importance however within the framework of the present invention. They will also be determined and executed within the framework of the present invention, which will be dealt with later, on the same way as is the case in the prior art. These translational positioning processes are thus not dealt with in any greater detail below.
Because of the fact that the machining heads 8, 9 are only able to be jointly positioned in at least one translational direction, the application program 19 and the computer program 15 must interoperate with each other such that the machining heads 9 are always positioned in the same way. The translational linear positionings PT and the rotational pivot positionings PS of the basic machining head 8 are thus simply accepted as corresponding positionings of the accessory machining head 9.
The method of operation of the prior art described above leads to satisfactory results if the machining heads 8, 9 are constructed identically and also tools which are carried by the machining heads 8, 9 are identically constructed. The identical nature of machining heads 8, 9 and tools can however not always be guaranteed. Furthermore the above-mentioned methodology is necessarily restricted to executing identical machining processes.